I have the Foxpro Spitfire. I did a complete review over on CoyoteGods.com. Although it worked pretty well at first, I started having trouble out of it. It would decide on it's own whether or not it wanted to change sounds when I asked it to.
I think it had a moisture problem since it is not sealed.
Also had problems with signal between remote and unit. This stems from the fact both have internal antennae. All in all, and although I am still using it, I would not buy it if I had it to do over again.
I don't have any experience with the Flextone calls. I am a little leery of them based on the price.
I'll end this by saying that I have had more success with mouth calls than electronics. An electronic repeats itself over and over and coyotes get wise really fast. I can make a mouth call sound different most every hunt and can change tones (by changing calls) much cheaper than changing electronic calls.
Good luck. Save some money and learn to use a mouth call first, just to see if you like doing this.